21400787 has 4 divisors (see below), whose sum is σ = 22331280. Its totient is φ = 20470296.

The previous prime is 21400781. The next prime is 21400793. The reversal of 21400787 is 78700412.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (21400781) and next prime (21400793).

It is a cyclic number.

It is not a de Polignac number, because 21400787 - 2⁶ = 21400723 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21400781) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 465212 + ... + 465257.

It is an arithmetic number, because the mean of its divisors is an integer number (5582820).

Almost surely, 2^21400787 is an apocalyptic number.

21400787 is a deficient number, since it is larger than the sum of its proper divisors (930493).

21400787 is an equidigital number, since it uses as much as digits as its factorization.

21400787 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 930492.

The product of its (nonzero) digits is 3136, while the sum is 29.

The square root of 21400787 is about 4626.0984641488. The cubic root of 21400787 is about 277.6365131969.

The spelling of 21400787 in words is "twenty-one million, four hundred thousand, seven hundred eighty-seven".